The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Active materials provide actuation with relatively low cost and mass. Active materials may include shape memory alloys (SMAs), electroactive polymers (EAPs), piezoelectric, magnetostrictive and electrorestrictive materials. By applying a current through the active material to increase the temperature or the magnetic field of the active material, an active material is capable of recovering strain developed from an exerted stress or load. The ability to recover strain enables the active material to provide actuation. In many applications, the active material is an SMA wire or cable. However, due to the thermal characteristics of SMA material, overload protection is essential to prevent the wire from overstretching, and thus, losing the ability to recover strain when activated.
It is known, for example, to use techniques such as mechanical overload protection. Mechanical overload protection requires additional assembly parts that may add to cost, package space restraints and weight.